Handheld audio devices, such as telephone handsets or other audio pick-up devices, are able to use two or more microphones to perform audio processing such as noise cancellation or echo cancellation upon signals picked up from a main microphone positioned on the device to detect a user's spoken voice. In many handheld audio devices, the main microphone, which is generally referred to below as a “voice microphone,” is located close to a central axis on the front of the handheld device to maintain a left-right symmetry for picking up the user's voice. The left-right symmetry provides similar audio pick-up performance with both left-handed and right-handed use. However, the industrial design of some electronic devices places other components on the central axis of the front of the handheld device, and displaces the voice microphone from such a location. In some instances, the voice microphone is asymmetrically located on the front of the handheld device, i.e., away from the central axis of the handheld device. This asymmetrical location of the voice microphone often results in disparate adaptive sound cancellation, such as echo or noise cancellation, performance between use of the handheld device when it is held to a right side or a left side of a speaker's face. Due to the likelihood that a right-handed user is likely to hold a handset on the left side of his or her face, and a left handed user is likely to hold a handset to the right side of his or her face, left-handed and right-handed users tend to experience different levels of echo or noise cancelling performance.
Some designs address this concern by including multiple microphones that are located on different portions of the handset where different subsets of those multiple microphones can be selected as a main voice pick-up microphone while others of those multiple microphones are selected as ambient noise microphones used to support adaptive sound cancellation processing. In those designs, some of those multiple microphones configured or selected to operate as voice pick-up microphones when the handset is held to the right side of a speaker's face, and others of those multiple microphones are configured to operate or are selected to operate as voice pick-up microphones when the handset is held to the left side of the speaker's face. The construction of devices with these multiple microphones increases the costs and circuit complexity of the device due to, for example, the additional microphones and the audio switching and selection processing that must be included.
Therefore, the performance adaptive sound cancellation processing based on ambient sounds detected by an ambient sound microphone that is applied to audio detected by another, asymmetrically placed voice pick-up microphone on a handset is able to be adversely affected based upon which side of the user's face a user is holding the handset.